Recently, polymer materials are increasingly utilized in various fields. Following such a tendency, corresponding to each need, besides properties of a polymer as a matrix, surface characteristics of the polymer are becoming important. For example, characteristics such as adhesion, cohesion, nonadhesiveness, antistatic properties, water-/oil-repellent properties, hydrophilicity, sliding properties and biocompatibility are required for the surface of a polymer.
Conventionally, various polymer surface modifying methods for imparting the above characteristics to the surface of a polymer are known (for example, Non-patent Document 1). For example, there is known a method for taking a physical measure represented by the irradiation of various energy rays, however, it requires cumbersome operations to become an expensive method (for example, Patent Document 1 and Patent Document 2).
The same applicants as those of the present invention disclose that as a polymer surface modifying method, by such a simple operation as mixing a highly-branched polymer to a matrix polymer made of a linear polymer, a highly-branched polymer can be concentrated on the surface and/or the interface of the matrix polymer (for example, Non-patent Document 2).
However, in this report, there is no description on distributing hydrophilic functional groups at the molecular ends of the highly-branched polymer in the outermost surface of a polymer structure at an enhanced density, and there is not indicated an action effect by this distribution.
In addition, for the purpose of modifying a polymer surface, there is known a method of adding or applying a highly-branched polymer, however, there is no description on distributing functional groups at the molecular ends of the highly-branched polymer in the outermost surface of a polymer structure at an enhanced density (for example, Patent Document 7, Patent Document 8 and Patent Document 9).
In addition, as one of polymer surface modifying methods, there is known a method of grafting a polymer chain through a polymerization initiating group formed in the surface of a solid (for example, Patent Document 3, Patent Document 4 and Patent Document 5). This surface modifying method by a surface graft polymerization can impart diverse surface characteristics by varying the type of a monomer to be polymerized. However, in these documents, a method of fixing a polymerization initiating group to the surface requires a cumbersome step such as the Langmuir-Blodgett method (LB method) and a chemisorption method, so that there has been desired a method capable of performing a polymer surface modification for a wider surface area by a simple step. In addition, a surface modifying method by fixing a dithiocarbamate group which is a photopolymerization initiating group to the polymer surface by the LB method or a chemisorption method to graft-polymerize the polymer, is publicly-known (for example, Patent Document 6).
However, in these documents, there is no description on technical methods and means of distributing hydrophilic functional groups at the molecular ends of a highly-branched polymer contained in a polymer structure and concentrated on the surface and/or the interface of the polymer structure in the outermost surface of the polymer structure at an enhanced density, so as to further graft polymer chains to the hydrophilic functional groups distributed in the outermost surface at an enhanced density. Also, there is no indication of advantageous effects obtained by these technical methods and means.
In addition, as a highly-branched polymer having a dithiocarbamate group at the molecular ends, there are known styrene-based hyperbranched polymers and acryl-based hyperbranched polymers (for example, Non-patent Document 3 and Non-patent Document 4).    Non-patent Document 1: Edited by Teruo Tsunoda, Kobunshi no Hyomenkaishitsu to Oyo (Surface Modification of Polymer and Application Thereof), published by CMC Publishing Co., Ltd. in June, 2001    Non-patent Document 2: Transactions of the Materials Research Society of Japan Vol. 32(1), p.p. 231 (2007)    Non-patent Document 3: Macromol. Rapid Commun. Vol. 21, p.p. 665 to 668 (2000)    Non-patent Document 4: Polymer International Vol. 51, p.p. 424 to 428 (2002)    Patent Document 1: JP-T-2005-511875    Patent Document 2: JP-T-2005-511876    Patent Document 3: Japanese Patent Application Publication No. JP-A-11-263819    Patent Document 4: JP-T-2002-145971    Patent Document 5: Japanese Patent Application Publication No. JP-A-2006-316169    Patent Document 6: Japanese Patent Application Publication No. JP-A-2006-113389    Patent Document 7: JP-T-2003-522266    Patent Document 8: JP-T-2003-529658    Patent Document 9: JP-T-2006-503947